The present invention relates generally to integrated circuit packages. More specifically, the invention relates to lead frames for the production of chip scale integrated circuit packages.
An integrated circuit (IC) package encapsulates an IC chip (die) in a protective casing and may also provide power and signal distribution between the IC chip and an external printed circuit board (PCB). An IC package may use a metal lead frame to provide electrical paths for that distribution.
To facilitate discussion, FIG. 1 is a top view of a lead frame panel 100 made up for a plurality of lead frames that may be used in the prior art. The lead frame may comprise leads 108, die attach pads 112, ties 116 for supporting the die attach pads 112, and a skirt 120 for supporting the plurality of leads 108 and ties 116. The lead frame panel 100 may be etched or stamped from a thin sheet of metal. IC chips 124 may be mounted to the die attach pads 112 by an adhesive epoxy. Wire bonds 128, typically of fine gold wire, may then be added to electrically connect the IC chips 124 to the leads 108. Each IC chip 124 may then be encapsulated with part of the leads 108 and the die attach pad 112 in a protective casing, which may be produced by installing a preformed plastic or ceramic housing around each IC chip or by dispensing and molding a layer of encapsulation material over all IC chips 124. FIG. 2 is a cross-sectional view of part of the lead frame panel 100 and IC chips 124. In a process described in U.S. patent application Ser. No. 09/054,422, entitled xe2x80x9cLead Frame Chip Scale Packagexe2x80x9d, by Shahram Mostafazadeh et al., filed Apr. 2, 1998, a tape 136 is placed across the bottom of the lead frame panel 100 and a dam 132 is placed around the lead frame panel 100. An encapsulation material 140 is poured to fill the dam 132, encapsulating the IC chips 124, the wire bonds 128, and part of the lead frame panel 100. The tape 136 prevents the encapsulation material 140 from passing through the lead frame panel 100. Once the encapsulation material 140 is hardened, the dam 132 and tape 136 may be removed. The encapsulation material 140 may be cut to singulate the IC chips 124 and leads 108.
It is desirable to provide an IC package process, which does not require the steps of adding tape to the lead frame and then removing the tape from the lead frame. It is also desirable to provide a process and lead frame that may accommodate various chip sizes and provides lead fingers.
To achieve the foregoing and other objects and in accordance with the purpose of the present invention, a variety of techniques is provided for packaging of integrated circuits. Generally, a conductive substrate formed from a conductive material is patterned to define a plurality of posts and a connecting sheet connecting the plurality of posts. Dice are physically mounted on a first portion of the plurality of posts, wherein each die is physically mounted on at least four posts. The dice are electrically connected to a second portion of the plurality of posts. A cap is molded over the plurality of dice and the patterned conductive substrate. The connecting sheet is then removed. Finally, integrated circuit packages are singulated.
Another aspect of the invention provides another method for packaging integrated circuits. Generally, a conductive substrate formed from a conductive material is patterned to define a plurality of posts and a connecting sheet connecting the plurality of posts. Dice are physically mounted on a first portion of the plurality of posts. The dice are electrically connected to a second portion of the plurality of posts. A cap is molded over the plurality of dice and the patterned conductive substrate. The posts are separated to form lead fingers from the separated plurality of posts.